This article presents a qualitative analysis method based on fuzzy relations for a cross-impact model designed for a technology impact assessment. The cross-impact knowledge is often uncertain or fuzzy when dealing with future events. Assessing the cross-impact relationships among future technologies creates a more uncertain or fuzzy situation because of the time and the uncertainty involved in evaluating future technologies. In addition, experts prefer to use Linguistic terms or fuzzy values in their predictions. Thus a cross-impact matrix is represented as fuzzy relations on causal concepts. We therefore develop inference algorithms based on fuzzy relations and show a simple technology assessment example to illustrate this approach. This approach is useful in finding the key technology because it considers not only the direct impact but also the indirect impact. (C) 1997 Elsevier Science Inc.